Programmed cell death (PCD) is a physiological process essential to the normal development and homeostatic maintenance of all multicellular organisms. PCD is of fundamental importance to biological processes ranging from embryogenesis to the development of the immune system. More recently, PCD has been shown to play an etiological role in cancer and birth defects resulting from exposure to ionizing radiation and/or teratogenic agents. Although the mechanism of mammalian apoptosis has not been elucidated, several lines of evidence indicate the involvement of a protease of the CED-3/ICE family. The prototypical member of this family is interleukin-1beta-converting enzyme (ICE), a cysteine protease that is inhibited by the cowpox virus-encoded inhibitor CrmA. Apoptosis of epithelial cells is CrmA inhibitable, suggesting that a CrmA-inhibitable ICE-like protease is a component of the death pathway The investigator has recently cloned a CED-3/ICE-related gene, designated YAMA, that specifically cleaves the DNA repair enzyme poly (ADP-ribose) polymerase (PARP) from its native 116 kDa form a characteristic 85 kDa fragment that is observed in many forms of PCD. Further, using purified components, the investigators demonstrated that the cleavage of PARP by YAMA was inhibited by CrmA, but not by an inactive point mutant of CrmA. Taken together the investigator's work suggests that YAMA represents an effector component of the cell death pathway. Given this, the specific aims are: (1) to obtain definitive evidence for the involvement of YAMA in apoptosis by inhibiting its synthesis and/or activity by antisense, dominant-negative and other inhibitory strategies; (2) since YAMA exists as a zymogen, determine if apoptosis stimuli trigger its processing to its active subunit forms. Further, define whether inhibitors of apoptosis, such as bcl-2, bcl-x and p35, attenuate YAMA processing; (3) As YAMA is expressed as a proenzyme, define upstream proteases responsible for its activation.